Transmitting intelligence by radiant energy



June 30, 1925.

Witnesses 1,544,081 F. K. VREELAND TRANSMITTING INTELLIGENCE BY RADIANT ENERGY Original Fil'ed Jan. 2, 1907' Inventor Atto rney Patented June 30, 1925.-

UNITED STATES ATEN OFFICE.

FREDERICK K. VREELAND, OF mon'rcmimnnw JERSEY, ASSIGNOR TO VREIELAN'D APPARATUS COMPANY, INC., OF NEW YORK, N. "Y., A. CORPORATION OF NEW YORK.

TRANSMITTING INTELLIGENCE BY BADIAN T ENERGY.

Original application filed January 2, 1907, Serial 11, 1917. Divided and this application To all whom z'tmay concern:

Be it known that I, FREDERICK K. VREE- LAND, a citizen of the United States, resid-- ing at Montclair, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Transmittin Intelligence by Radiant Energy, of which the following is a description.

The present application is a division of my application for Letters Patent filed January 2, 1907, Serial No. 350,476, issued as Patent No. 1,239,852, dated Sept 11, 1917, relating to receivers of electrical impulses.

The signals produced by an ordinary spark transmitter are intermittent in character and consist of a series of strongly damped wave-trains. following each other in rapid succession, and separated by intervals of inacti ity. The class of signal impulses to which this invention relates particularly, are preferably undamped oscillations ofconstant intensity, which are broken up into signal impulses by interrupting the wave train, by varying its fre quency, or otherwise altering its character. Instead of an absolutely undamped oscillation, it is possible to use an oscillation .of somewhat varying intensity, provided this is sufficiently sustained to have a reasonably constant effect upon the receiving apparatus during a sufficiently large num-' ber of successive oscillations;

.Any suitable form of electrical oscillator producing sustained high frequency oscillations may be employed for the signal and local oscillations, such for example, as the oscillator describedin my Patent No. 829,934.

The signal produced by an undamped oscillator or other generator. of practically continuo'us sustained oscillations is not suited to observation by ordinary telephonic receivers. If a given signal impulse is practically continuous and constant in intensity, its effect upon the telephonic receiver is simply to produce a click at the beginning and a click at the. end of the impulse, these clicks being inconspicuous and difiicult to observe.

Various methods have No..350,476, Patent No. 1,239,852, dated September filed October 27, 1915. Serial No. 58,100.

- been proposed for breaking up such a sigtivity when the two oscillations assist each other, separated by intervals of rest, or of minimum activity, when the two oscillations are, mutually destructive.

This interference may be accomplished by impressing the signal impulses and locally generated oscillations upon the same oscillating circuit, or by otherwise combining the effect of the signal and local oscillations, thus producing surges of varying intensity, which are detected by a suitably arranged detector and indicator, as I will hereafter describe and claim.

In this specific embodiment of my invention I prefer to use as a detector an electrolytic cell of the type to which I apply the name polariphone and'which I describe in United States Patents Nos. 780,842 (dated J anuary 24, 1905). and 783,712 (dated February 28, 1905), that device, as is well known, producing a rectification of the waves, and thus permitting an ordinary magnetic telephone to be used as the indicator giving off a musical note of a ,pitch' corresponding to the rate of the surges or beats, due to the superposition of the signal and local oscillations. -This production of beatsafi'ords a peculiarly delicate means of of the beats or surges depends upon the difference of the fre uencies of the signal impulses andof the ocally generated oscilla tions; Hence, a very slight variation in the former will produce a correspondingly large variation in the differential or beat frequency. Thus two sending stations whose frequencies are so nearly the same that ordinary methods of tuning would not discriminate between them may be readily distinguished from each other by the comparatively large difference in pitch of the note produced by the beats. If this note is of audible frequency, the discrimination may be made by the ear, or it may be made automatically by mechanically tuning the receiver to respond to a definite beat frequency by any of the well known methods.

In the original application (of which the present caseis a division) in addition to claiming my invention in generic terms, regardless of the class or character of detector employed, I have also presented specific claims covering the use of an electro mechanical detector (for instance, an electro static telephone) interposed in a common circuit in which the beats are produced.

I propose to describe and claim in the present divisional application, a modification of the invention, in which an ordinary magnetic telephone may be used as the receiver or indicator, in which case I employ a detector for rectifying or translating the waves representingthe beats or surges, so that they may be caused to influence the telephone diaphragm and cause it to vibrate with a musical note.

As in the original application, I combine the received si al impulses with locally generated sustained oscillations in a common circuit or common element of a circuit, producing by this combination a resultant complex oscillation or wave-train which is used to afi'ect the detector. If there is a slight difference of frequency between the two oscillations there will be certain periods when they are in synchronism and re-inforce each other, and other periods when they are in opposition and tend to annul each other. The result will be a periodic fluctuation in the intensity of the resultant oscillation, producing beats whose frequency depends upon the difference in frequency of the two oscillations. Thus, a long sustained signal impulse which would ordinarily be observed in a telephone as a click at the beginning and a click at the end of a signal, is now broken up-intoa vibratory force which gives a continuously audible note in the telephone associated with the detector. The pitch of this audible note may be varied at will by varying the frequency of the local or of the signal oscilla- 'tions. For example, in the case of a wireless telegraph transmitter sending out signals at a frequency of 100,000 cycles per second, if the oscillator at the recelving station which supplies the exciting current or voltage has a frequency differing from this by one per cator T and t cent, say, 99,000cycles, the resultant beats will have a frequency of cycles per second, which is a high-pitched musical note. If the frequency of the local ter understood, attention is directed to the accompanying drawing, forming part of this specification, and in which Figure 1 is a diagrammatic view of a wireless receiver embodying my present invention, wherein the detector and indicator are connected directly to the resonant circuit; Figure 2, a corresponding View, in which the detector is connected directly to the resonant circuit,

the telephone or other indicator being located in a separate tuned receiving circuit; and Figure 3 a diagram of my improved oscillator, which I prefer to use for the source of local oscillations. 25 is the antenna or collecting circuit. A resonant circuit, CLSS is coupled with the antenna or collecting circuit, and comprises the condenser C, the tuning inductance L, the secondary S of a transformer PS coupling the resonant circuit and the antenna circuit, and a secondary coil S, which is inductively coupled to the local oscillator O. The oscillator O is preferably of the type described in my patent No. 829,934, but obviously any other suitable source of local oscillation can be used. The frequency of such an oscillator is very easily controlled by varying the capacity or inductance of the resonant circuit of the oscillator and the exciting oscillations are thus brought into synchronism with the si nal impulses or caused to produce beats of any desired frequency. The coupling of the secondary coil S to the oscillator need not be close; it is uusally sufficient to have the oscillator simply operating in the same room as the resonant circuit, as the latter is exactly or very nearly in tune .with the oscillator. The resonant circuit is tuned to the signal impulses by adjusting the capacity of the condenser or by varying the inductance of the circuit, as by varying the self-induction of the coil L,'or one or both of the secondar coils SS. The detector R, which is pre erably of the polari hone type, as, described in my Patents No. 80,842 and No. 783,712, with its associated apparatus, includin the ordinary teleqlhone receiver or other indie battery B, and potentiometer A, is preferably shunted across a portion of the resonant circuit, where it is subjected to a high potential difference without imposing its high resistance in the path of the oscillations. It is thus afiected by the beats resulting from the superposition of the two sets of oscillations in the resonant circuit, and by reason of the capacity of the detector to rectify'high frequency oscillations, these beats are converted into a form suitable for affecting the telephone receiver T, being heard therein as a musical note of a pitch corresponding to the rate of the beats.

The method of breaking up a continuous or undamped signal-impulse into an intermittent one by causing it to produce beats with the current from a local generator of continuous oscillations slightly out of tune with the signal impulses, may be applied to a great variety of detectors. My system is selective by virtue of. the resonance of the tuned circuit CLSS' to the signal oscillations, but. a further degree of selectivity may be attained by mechanically tuning the receiver, as by loading the diaphragm in the manner well understood, so that it will vibrate only at a definite frequency. The apparatus is then adjusted so that the frequency of the beats is the same as the natural frequency of the telephone. In this manner an exceedingly high degree of selectivity may be attained, for, as the frequency of the beats depends upon the difference of frequencies of the signalimpulses and of the local oscillations, the slightest variation in either will produce a large change in the frequency of the beats.

Figure 2 represents an arrangement similar to that of Figure 1, in which a system of electrical tuning to the beat frequency is substituted for mechanical tuning. The local circuit of the detector R is coupled through a transformer P S to an oscillating circuit tuned electrically to the frequency of the beats, and including the telephoneor other indicating device T. Or both electrical and mechanical tuning may be employed simultaneously.

Having thus described my invention, and illustrated its use, what I claim is:

1. The method of receiving oscillating current energy by first combining it with the energy of a separately produced auxiliary oscillating current whose frequency is.

slightly different from the frequency of the received current, and then rectifying and utilizing the combined current to operate an indicator.

2. The method of wireless signaling which comprises exciting a receiving circuit by the received wave energy and also by an auxiliary alternating current of a frequency so related to the frequency of the received energy as to produce beats therewith, and

then rectifying and using this composite current to operate a receiving instrument, whereby to amplify the effect of the received signal.

3. The method of Wireless signaling which comprises the constant production of an auxiliary oscillating current of frequency of said two currents, and an indicator operated by the rectified current.

5. A receiver for wireless signaling, comprising an antenna, a cumulatively and proportionally responsive detector associated therewith, a current operated indicator, and an independent cooperating source of current also associated with the antenna and having a frequency difi'ering slightly from the frequency of the received signaling current, so as to produce beats therewith and thereby operate the indicator by the combined currents.

6. In wireless signaling apparatus the combination with the receiving circuits, a detector and a current operated indicator, of a local means to generate a co-operating current and produce beats with the current of the receivedwaves, whereby to control the character of the signal note during the receipt of messages, substantially as described.

This specification signed and witnessed this 26th day of October, 1915.

FREDERICK K. VREELAND.

Witnesses:

ANNA E. BENTON, CHAS. Sommmrm. 

